Best thing we ever did for our timid pup was take her thru obedience classes. You know, the kind at Petsmart or Petco. After initial beginner training I took her thru a class called "Click-a-Trick". This was more training but very FUN for both myself and the dog..... it really helped her open up and get used to being out around people. She also got so much positive feedback from all the tricks she learned that she began to love to show off for new people.
Maybe this same approach will help for you.
Maybe this same approach will help for you.